U.S. patent number 8,721,992 [Application Number 11/905,931] was granted by the patent office on 2014-05-13 for micro fluidic device.
This patent grant is currently assigned to Fuji Xerox Co., Ltd. The grantee listed for this patent is Masaki Hirota, Kazuaki Tabata, Seiichi Takagi, Takayuki Yamada. Invention is credited to Masaki Hirota, Kazuaki Tabata, Seiichi Takagi, Takayuki Yamada.
United States Patent |
8,721,992 |
Yamada , et al. |
May 13, 2014 |
Micro fluidic device
Abstract
A micro fluidic device comprises a micro channel in which a
plurality of fluids form laminar flows and are supplied, wherein an
inner wall of the micro channel comprise a protruding part that is
substantially parallel to the flows of the fluids and protrudes in
directions substantially vertical to interfaces formed by the
plurality of fluids.
Inventors: |
Yamada; Takayuki (Kanagawa,
JP), Hirota; Masaki (Kanagawa, JP), Tabata;
Kazuaki (Kanagawa, JP), Takagi; Seiichi
(Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Yamada; Takayuki
Hirota; Masaki
Tabata; Kazuaki
Takagi; Seiichi |
Kanagawa
Kanagawa
Kanagawa
Kanagawa |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
Fuji Xerox Co., Ltd (Tokyo,
JP)
|
Family
ID: |
39794706 |
Appl.
No.: |
11/905,931 |
Filed: |
October 5, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080240987 A1 |
Oct 2, 2008 |
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Foreign Application Priority Data
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Mar 27, 2007 [JP] |
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2007-080768 |
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Current U.S.
Class: |
422/503; 422/501;
422/502; 436/180; 422/504 |
Current CPC
Class: |
B01L
3/502707 (20130101); B01L 3/502776 (20130101); B01J
19/0093 (20130101); B01L 2300/0816 (20130101); B01J
2219/00828 (20130101); Y10T 436/2575 (20150115); B01J
2219/00824 (20130101); B01L 2300/0887 (20130101); B01J
2219/00783 (20130101); B01J 2219/0086 (20130101); B01L
2400/086 (20130101); B01L 2200/0636 (20130101); B01J
2219/00822 (20130101); B01L 2300/0877 (20130101) |
Current International
Class: |
B01L
3/00 (20060101); G01N 1/10 (20060101) |
Field of
Search: |
;422/99,100,500-505
;436/180 |
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Primary Examiner: Kwak; Dean
Attorney, Agent or Firm: Oliff PLC
Claims
What is claimed is:
1. A micro fluidic device, for use with a plurality of fluids,
comprising: a substrate; a plurality of thin film pattern members
formed on the substrate, the thin film pattern members comprising
nickel, an alloy including nickel as a main component, copper or an
alloy including copper as a main component; a plurality of inlet
ports; a plurality of introduce channels to which the inlet ports
are connected; and a micro channel, formed on the substrate, to
which the introduce channels are joined so as to form a division
between the introduce channels perpendicular to a plane on which
the substrate extends, and defining an inner wall of the micro
channel, the micro channel including: a curved portion having a
first end, a second end, and a center disposed between the first
and second ends; a plurality of protruding parts connected to the
inner wall of the micro channel extending beyond the inner wall in
a direction substantially parallel to the plane on which the
substrate extends, each extending from the first end of the curved
portion to the second end of the curved portion on a plane
substantially parallel to the plane on which the substrate extends,
and protruding in a direction substantially parallel to the plane
on which the substrate extends, wherein the heights of the
plurality of protruding parts increase as the plurality of
protruding parts extend from the first end of the curved portion to
the center of the curved portion; the plurality of protruding parts
are provided only in the inner wall of an outer peripheral side of
the curved portion of the micro channel; the heights of the
plurality of protruding parts decrease as the plurality of
protruding parts extend from the center of the curved portion to
the second end of the curved portion; the heights of the plurality
of protruding parts at the center of the curved portion are greater
than the heights of the plurality of protruding parts at the first
and second ends of the curved portion; and the heights of the
plurality of protruding parts are 50% or smaller than a width of
the micro channel.
2. A micro fluidic device according to claim 1, wherein the micro
fluidic device is formed by laminating thin film pattern members.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on and claims priority under 35 USC 119
from Japanese Patent Application No. 2007-080768 filed Mar. 27,
2007.
BACKGROUND
(i) Technical Field
The present invention relates to a micro fluidic device, and more
particularly to a micro fluidic device having a micro channel and a
method for producing the micro fluidic device.
(ii) Related Art
In micro channel, since fluids are apt to form laminar flows and
easily flow, the laminar flows can be formed in which two liquids
flow under a state that they are not mixed and kept separated from
each other. To increase a contact time between the fluids, the
channel needs to be lengthened. In a restricted space, curved
places are provided to fold the channel and lengthen the channel.
However, in the curved place, a convection called a Dean vortex is
generated due to a centrifugal force (see Shinichi Ohkawara and
other three members, chemical Engineering Theses, Vol. 30, No. 2,
p. 135 to 140 (2004)).
Especially, in the laminar flows having micro particles dispersed,
the micro particles move to the outside wall at the curved place so
that an unexpected mixture or a mal-distribution of the particles
is liable to arise.
SUMMARY
According to an aspect of the invention, there is provided a micro
fluidic device comprising a micro channel in which a plurality of
fluids form laminar flows and are supplied, wherein an inner wall
of the micro channel comprise a protruding part that is
substantially parallel to the flow direction of the fluids and
protrudes in directions substantially vertical to interfaces formed
by the plurality of fluids.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the present invention will be described in
detail based on the following figure, wherein:
FIG. 1 is a schematic plan view showing an exemplary embodiment of
a micro fluidic device of the present invention;
FIG. 2 is an enlarged view including a curved place of the micro
fluidic device shown in FIG. 1;
FIGS. 3A to 3C are sectional views taken along a line X-X' of the
micro fluidic device shown in FIG. 2;
FIGS. 4A to 4E are sectional views of the micro fluidic device
shown in FIG. 2;
FIGS. 5A and 5B are sectional views showing another example of a
curved place in the micro fluidic device of the present
invention;
FIGS. 6A to 6C are explanatory views of thin film patterns for
forming a part shown in FIG. 2; and
FIGS. 7A to 7F are fabrication process diagrams showing one
exemplary embodiment of a method for fabricating a micro fluidic
device preferably usable for the present invention.
DETAILED DESCRIPTION
A micro fluidic device of the present invention has a micro channel
in which a plurality of fluids form laminar flows and are supplied
and is characterized in that protruding parts are formed on the
inner walls of the micro channel that are substantially parallel to
the flow direction of the fluids and protrude in directions
substantially vertical to interfaces formed by the plurality of
fluids.
Since the micro fluidic device includes the protruding parts formed
on the inner walls of the micro channel that are substantially
parallel to the flow direction of the fluids and protrude in the
directions substantially vertical to the interfaces formed by the
plurality of fluids, the laminar flows of the flows are held, and
an unexpected mixture or a mal-distribution of particles in the
fluids hardly arises. Therefore, the stable laminar flows can be
obtained.
The micro fluidic device of the present invention is not especially
limited to a use and may be usable for various kinds of well-known
uses. A channel length, a flow velocity, a kind of fluid,
temperature or the like are preferably suitably selected depending
on the use. Specifically, the micro fluidic device may be used as
an analyzing device in a medical field, producing, classifying and
cleaning devices of micro particles and a chemical reaction device,
for instance, a synthesizing device or a polymerizing device.
In the present invention, the micro channel means a very small
channel for supplying an extremely small quantity of liquid or gas
and the width thereof is located within a range of several .mu.m or
more to several thousand .mu.m or smaller. In the present
invention, the micro channel means a channel of a micro-meter scale
and further includes a channel of a milli-meter scale.
The width of the channel may be suitably selected depending on a
purpose. A range of 10 .mu.m or more to 1000 .mu.m or smaller is
preferable and a range of 20 .mu.m or more to 500 .mu.m or smaller
is more preferable.
In the present invention, since the micro channel is of the micro
scale, both a dimension and a flow velocity are small. The Reynolds
number (Re) of the fluids flowing in the micro channel is 2,300 or
smaller. Accordingly, the micro fluidic device having the micro
channel of the micro scale is not governed by turbulent flows, but
by the laminar flows.
Here, the Reynolds number is represented by a below-described
equation. When the Reynolds number is 2,300 or smaller, the micro
fluidic device is governed by the laminar flows. Re=uL/.nu. (u:
flow velocity, L: length, .nu.:coefficient of kinematic
viscosity)
To maintain governance by the laminar flows, the micro fluidic
device of the present invention has the protruding parts formed on
the inner walls of the micro channel that are substantially
parallel to the flow direction of the fluids and protrude in the
directions substantially vertical to the interfaces formed by the
plurality of fluids.
In the micro fluidic device of the present invention, the plurality
of fluids form the laminar flows and are supplied. In the micro
fluidic device, two or more fluids are preferably supplied from a
plurality of fluid inlet ports and a merged part forming the
laminar flows is preferably provided. Further, the micro fluidic
device of the present invention includes one or more outlet ports
and preferably has a plurality of outlet ports corresponding to the
laminar flows.
In the present invention, the micro channel is a channel that has a
very small diameter and is isolated from an outer part by a base
material. The base material may be a base board or a tubular
material.
In the present invention, the form of the micro channel is not
especially limited, however, ordinarily is tubular. Further, a
sectional form of the micro channel is not especially limited and
any of forms may be employed. As a sectional shape of a plane
intersecting at right angles to the axis of a channel of the micro
channel, exemplified are a circular form, an elliptical form, a
semi-circular form, a rectangular form, a triangular form, other
polygonal forms, a tumbler form. However, the present invention is
not limited thereto. The sectional shape of the micro channel is
preferably rectangular among them, because the micro fluidic device
can be easily manufactured.
Further, in the present invention, a part or all of the micro
channel includes the protruding parts formed on the inner walls
that are substantially parallel to the flow direction of the fluids
and protrude in the directions substantially vertical to the
interfaces formed by the fluids. That is, in the present invention,
the micro channel is preferably a micro channel that has the
protruding parts in a part of the inner walls and the rectangular
sectional shape.
Further, in the present invention, the shape of the axis of the
channel is not especially limited and any of forms such as a
straight line or a curve may be employed. Here, the form of the
axis of the channel means an axis of a flowing direction of the
fluid in the micro channel.
As described above, the shape of the axis of the channel is not
especially limited. However, to ensure a channel length for a
prescribed area, a curved place is preferably formed. The curved
place means a part that changes the direction of a flow by
providing a folded shape, a circular arc shape or an angled shape
in the axis of the channel of the micro channel. Particularly, in
the present invention, the curved place preferably has the circular
arc shape. As one example of the circular arc shape, the
semi-circular form may be exemplified.
Namely, the form of the axis of the channel entirely includes the
straight line part and the curved place and is preferably designed
so that the channel length of the micro channel is large in the
prescribed area.
The forms of the protruding parts provided on the inner walls of
the micro channel are not especially limited, however, they are
provided to be substantially parallel to the flow direction of the
fluids. In the present invention, the protruding parts are provided
to be substantially parallel to the flow direction of the fluids,
however, the protruding parts do not need to be exactly parallel to
the flow direction of the fluids and an angle can be selected
within such a range as not to prevent the flows of the fluids. In
the present invention, "substantially parallel to the flow
direction of the fluids" means an angle of 10 degrees or smaller
with respect to the flow direction of the fluids. The angle is
preferably 5 degrees or smaller, more preferably 3 degrees or
smaller and furthermore preferably 0 degree with respect to the
flow direction of the fluids, namely, parallel to the flow
direction of the fluids.
For instance, when the sectional forms of the micro channel
vertical to the flow direction of the fluids are rectangular, one
protruding part preferably protrudes from one side at right angles
to an inner part of the channel. Further, when an opposed
protruding part is provided, the other protruding part preferably
similarly protrudes at right angles to an opposite side from a
corresponding position on the opposite side. Further, as described
below, the protruding parts protrude substantially vertically to
the interfaces formed by the fluids.
In the present invention, the protruding parts provided in the
inner walls of the micro channel protrude substantially in vertical
directions to the interfaces formed by the plurality of fluids. In
the present invention, the protruding parts are provided
substantially vertically to the interfaces formed by the fluids,
however, the protruding parts do not need to be exactly vertical to
the interfaces, and an angle can be selected within such a range as
not to prevent the deformation of the interfaces of fluids. In the
present invention, "protrude in the directions substantially
vertical to the interfaces formed by the plurality of fluids" means
that a deviation from an angle of 90 degrees is an angle of 10
degrees or smaller. The deviation from the angle of 90 degrees is
preferably 5 degrees or smaller, more preferably 3 degrees or
smaller and furthermore preferably 0 degree with respect to the
interfaces formed by the fluids, that is, right angled to the
interfaces.
When three or more laminar flows are formed and two or more
interfaces are present, the protruding parts may protrude in the
directions substantially vertical to at least one interface,
however, more preferably protrude in the directions substantially
vertical to all the interfaces and the interfaces are preferably
formed so as to satisfy the above-described conditions.
As the shapes of the protruding parts, flat plate shapes may be
employed, or the height of the protruding parts may be decreased or
increased more toward the end of the channel from the inner walls.
Further, the height of the protruding parts may be gradually
increased or decreased more toward the direction of the axis of the
channel. As the shapes of the protruding parts, the protruding
parts preferably have the same height from the inner walls to the
end of the channel and have the rectangular shapes on the
perpendicular plane to the axis of the channel, and rectangular
plate forming protruding parts are more preferably provided among
them.
Here, the "protruding parts" mean plate-shaped structures that
stick out from the inner walls of the channel and extend in the
directions of the axis of the channel.
Further, the protruding parts may be provided continuously in the
directions of the axis of the channel from the inlet ports to the
outlet ports of the channel and may be interrupted halfway.
Further, the protruding parts may be provided at any part of the
section of the channel and provided on an upper surface and a lower
surface depending on the directions of the interfaces formed by the
laminar flows. However, the protruding parts are preferably
provided in the direction of the axis of the channel at parts
corresponding to the inner walls of an outer peripheral side of the
curved places of the channel and the inner walls of an inner
peripheral side thereof. Namely, the protruding parts are
preferably provided in the inner walls of the channel in the outer
peripheral side and the inner peripheral side of the curved places
in terms of a centrifugal force. At this time, the laminar flows
are formed in the side-by-side manner, which means outer peripheral
side and the inner peripheral side.
In the present invention, the protruding parts are preferably
provided only in the curved places and more preferably provided
only in the inner walls of the outer peripheral side of the curved
places of the channel. When the protruding parts are arranged as
described above, convection in the curved places can be preferably
prevented to more stabilize the laminar flows and restrain the
fluids to being mixed.
Only one protruding part may be provided and a plurality of
protruding parts may be provided in the inner wall of the channel.
Namely, a plurality of parallel protruding parts may be provided on
the same section in the channel. In such a case, one or more to
five or smaller protruding parts are preferably provided and one or
more to three or smaller protruding parts are more preferably
provided.
That is, in the present invention, the plurality of protruding
parts is preferably provided in the inner walls of the outer
peripheral side of the curved places of the channel. Especially, in
the case of the micro fluidic device having a plurality of curved
places, the plurality of protruding parts are preferably provided
in the inner walls of the outer peripheral side of all the curved
places.
The height of the protruding part is preferably 50% or smaller as
wide as the width of the channel. Here, the "height of the
protruding part" means the height of the protruding part when it is
assumed that a width from the inner wall of the channel to the
inner wall of the channel opposed thereto in the direction vertical
to the axis of the channel is set to 100%. The height of the
protruding part is more preferably set to 5% or more to 50% or less
and furthermore preferably set to 10% or more to 25% or less.
The height of the protruding part is preferably set to 50% or less
as wide as the width of the channel so that stable laminar flows
can be obtained.
Now, the present invention will be described in detail by referring
to FIGS. 1 to 7F.
The same reference numerals used below designate the same
components.
FIG. 1 is a schematic plan view showing a preferred example of the
micro fluidic device of the present invention.
In a substrate 22, a micro channel 20 is provided. In the micro
channel 20 of the micro fluidic device 10, inlet ports 24A and 24B
for introducing a fluid A and a fluid B respectively, and outlet
ports 26A and 26B for discharging the fluid A and the fluid B
respectively, are provided.
In FIG. 1, an exemplary embodiment for introducing the two fluids
is shown, however, the present invention is not limited thereto and
three or more fluids may be introduced. Further, one kind of the
fluids may be a micro particle dispersion liquid and the micro
fluidic device may be used as a classifying device of micro
particles or a cleaning device of micro particles. As the fluid,
both gas and liquid can be used. In the present invention, as the
fluid, the liquid is preferable.
In FIG. 1, the two liquids (the fluid A and the fluid B) are
introduced from the inlet ports 24A and 24B and supplied to one
micro channel 20 as laminar flows. In FIG. 1, the two liquids (in
FIG. 1, the fluid A and the fluid B) supplied to the micro channel
20 subsequently flows in one merged channel as the laminar
flows.
Then, the fluid A and the fluid B are respectively discharged from
the outlet ports 26A and 26B. In the present invention, the number
of the outlet ports is not especially limited and one or more
outlet ports may be provided and the number of the outlet ports may
be suitably selected depending on its purpose. Further, a plurality
of outlet ports may be provided along the channel or the outlet
ports may be separately provided on upper and lower parts of the
channel.
In FIG. 1, to form the micro channel having a sufficient length on
the substrate of the same area, a curved place 30 is provided.
Other positions except the curved place form a straight line part
32. However, the micro fluidic device of the present invention is
not limited thereto, and, for instance, a curved place such as a
zigzag part may be provided.
FIG. 2 is an enlarged view including the curved place of the micro
fluidic device shown in FIG. 1.
In FIG. 2, the fluid A is supplied in an outer peripheral side of
the curved place 30 of the channel and the fluid B is supplied in
an inner peripheral side of the curved place 30 of the channel. An
interface 55 is formed between the two fluids.
FIG. 3A shows a cross-sectional view taken along a line X-X' of the
micro channel shown in FIG. 2. In FIG. 3A, the micro channel 20
includes an inner wall 40 in the inner peripheral side of the
curved place, an inner wall 42 in the outer peripheral side of the
curved place, an upper wall 44 and a lower wall 46 and has a
channel width W.
In a usual micro channel (see FIG. 3C), since a protruding part is
not provided, an unexpected mixture (shown by arrow marks) of a
fluid A and a fluid B arises due to a centrifugal force in a curved
place so that the fluid A and the fluid B passing the curved place
are mixed together in an interface between them.
FIG. 3A shows one example of a cross-sectional view of the micro
channel 20 at the curved place 30 of the micro fluidic device 10 of
the present invention. Here, the fluid A and the fluid B are
supplied and curved from a front side of this sheet to an interior
to form the interface 55. In the inner wall 40 in the inner
peripheral side at the curved place of the micro channel 20 and the
inner wall 42 in the outer peripheral side at the curved place,
rectangular plate shaped protruding parts 50 are provided that are
parallel to the flow direction of the fluids and vertical to the
interface 55.
In FIG. 3A, three pairs of the protruding parts 50 are provided in
parallel with the flow direction of the fluids, however, the
present invention is not limited thereto. One or more protruding
parts 50 may be provided and the number of the protruding parts to
be provided may be preferably selected so as to obtain stable
laminar flows. Further, as described above, the sectional form of
the protruding part may be designed so that the height thereof is
increased from the curved place to the inner part of the channel or
conversely decreased from the curved place to the inner part of the
channel.
Further, the height W' of the protruding part provided in the inner
wall in the outer peripheral side at the curved place and the
height W'' of the protruding part provided in the inner wall in the
inner peripheral side at the curved place are preferably
respectively 50% or smaller as high as the channel width W, more
preferably 5% or more to 50% or less and furthermore preferably 10%
or more to 25% or less. The height of the protruding parts is
preferably located within the above-described range, so that the
stable laminar flows can be maintained.
Further, as W' and W'', the same height may be used or different
height may be selected.
Further, as shown in FIG. 3A, when the protruding parts are
provided in both the opposed inner walls, the total of the height
of the protruding parts (W'+W'') is preferably 60% or smaller as
high as W, more preferably 10% or more to 50% or less, and
furthermore preferably 20% or more to 40% or less. The total of the
height of the protruding parts is preferably located within the
above-described range, so that the stable laminar flows can be
formed without decreasing the velocity of the laminar flows.
As shown in FIG. 3A, when the protruding parts are provided in both
the opposed inner walls, the opposed protruding parts may be
provided at any positions, and may be preferably provided in
parallel. That is, the protruding parts are preferably provided so
as to have the same height with respect to the direction of height
(in FIGS. 3A to 3C, a direction for connecting the upper surface to
the lower surface) from the substrate of the micro channel. The
protruding parts are preferably arranged as described above, so
that the stable laminar flows can be formed.
The thickness a of the protruding part and a space b between the
protruding parts can be suitably selected depending on a purpose
and preferably suitably selected so as to obtain the stable laminar
flows. W'/b is preferably 3 or smaller and more preferably 1.5 or
smaller.
Further, as shown in FIG. 3A, when the plurality of protruding
parts 50 are provided, the shapes of the protruding parts, the
height W' and W'' of the protruding parts and the thickness a of
the protruding parts may be respectively the same or different and
preferably suitably selected. Further, when three or more
protruding parts are provided, the space b between the two or more
protruding parts may be respectively the same or different and
preferably suitably selected.
FIG. 3B shows another preferred example of a section taken along a
line X-X' of FIG. 2.
In FIG. 3B, the protruding parts 50 are provided only in the inner
wall in the outer peripheral side of the curved place. In this
case, the height W' of the protruding part 50 is preferably set to
50% or smaller as high as the width W of the micro channel 20. The
height W' of the protruding part 50 is preferably located within
the above-described range so that a convection due to the
centrifugal force can be prevented and the stable laminar flows can
be formed.
The above-described preferred height of W' and W'' means a maximum
height and the maximum height of the protruding parts provided in
the micro channel is preferably located within the above-described
range. As described below, the protruding part having the maximum
height in a central part of the curved place is preferable.
The protruding parts 50 are not limited to the above-described
protruding parts and may be provided in the upper surface 44 or the
lower surface 46 of the micro channel 20 as described below.
However, for the purpose of obtaining the stable laminar flows, the
protruding parts 50 are preferably provided in the inner wall 40 in
the inner peripheral side of the curved place and/or the inner wall
42 in the outer peripheral side of the curved place as shown in
FIG. 3A or FIG. 3B. Especially, as shown in FIG. 3B, the protruding
parts are preferably provided in the inner wall 42 in the outer
peripheral side of the curved place as shown in FIG. 3B.
In the present invention, the protruding part provided in the
curved place is preferably provided in such a way that the height
of the protruding part reaches a maximum at the center of the
curved place, and the height of the protruding part becomes
gradually lower toward the both ends of the curved place.
Now, a description will be given by referring to FIG. 4A to 4E.
FIGS. 4A to 4E show sectional views of the micro channel shown in
FIG. 2. FIG. 4A shows a section taken along a line M-M' before the
curved place 30. In this section, the protruding part is not
provided. The protruding part is provided so that its height is
gradually increased from the part before the curved place. In a
section taken along a line N-N' shown in FIG. 4B, the protruding
parts having low height are provided. In a section (FIG. 4C) taken
along a line X-X' at the center of the curved place, the height of
the protruding parts is the highest. Further, the height of the
protruding parts is provided so as to be gradually low toward the
end of the curved place. In a section taken along a line P-P' shown
in FIG. 4D, the protruding parts are provided that have the height
lower than that of the section taken along the line X-X'. Further,
as shown in FIG. 4E, in a section taken along a line Q-Q' as the
finish of the curved place, the protruding part is not provided.
Namely, assuming that in the N-N' section, the X-X' section and the
P-P' section, the height of the protruding parts provided in the
inner wall in the outer peripheral side is respectively Wb', Wc',
and Wd' and the height of the protruding parts provided in the
inner wall in the inner peripheral side is respectively Wb'', Wc'',
Wd'', relations of Wb'<Wc'>Wd' and Wb''<Wc''>Wd'' are
established.
Now, referring to FIGS. 5A and 5B, one exemplary embodiment of the
micro fluidic device of the present invention will be described in
which two fluids are supplied in upper and lower parts on a section
vertical to a direction of an axis of a channel.
FIG. 5A is another example showing a section of a channel in a
curved place of the micro fluidic device of the present
invention.
In FIG. 5A, two fluids designated by a fluid A and a fluid B form
laminar flows and are curved and supplied from a front side of a
sheet surface to an interior. FIG. 5A shows the section of the
channel in the curved place and the channel 20 includes an inner
wall 40 in the inner peripheral side of the curved place, an inner
wall 42 in the outer peripheral side of the curved place, an upper
surface 44 and a lower surface 46.
In the inner wall of the channel, protruding parts 50 are provided
that protrude in the directions vertical to an interface 55 formed
by the fluid A and the fluid B. The protruding parts 50 are formed
in parallel with the flow direction of the fluids and curved from
the front side of the sheet surface to the interior in FIG. 5A.
The height W2' and W2'' of the protruding parts to be formed is
respectively 50% or smaller as high as a channel width W2, more
preferably 5% or more to 50% or less and furthermore preferably 10%
or more to 25% or less. The height of the protruding parts is
preferably located within the above-described range, so that the
stable laminar flows can be maintained. Further, as W2' and W2'',
the same height may be used or different height may be
selected.
Further, as shown in FIG. 5A, when the protruding parts are
provided in both the opposed inner walls, the total of the height
of the protruding parts (W2'+W2'') is preferably 60% or smaller as
high as the width W2 of the channel, more preferably 10% or more to
50% or less, and furthermore preferably 20% or more to 40% or less.
The total of the height of the protruding parts is preferably
located within the above-described range, so that the stable
laminar flows can be formed without decreasing the speed of the
laminar flows.
Further, the width a of the protruding part and a space b between
the protruding parts can be suitably selected as described
above.
Further, when the two upper and lower laminar flows are formed, the
height of the protruding parts is preferably provided so as to be
maximum in the center of the curved place. The state thereof is
described above.
FIG. 5B shows a secondary flow velocity vector generated in the
section of the channel shown in FIG. 5A. As shown in FIG. 5A, when
the fluids are arranged in the upper and lower parts, a pair of
Dean eddies are formed in the upper and lower parts. An area where
a secondary flow velocity is the highest is located in the
intermediate parts of the upper and lower Dean eddies. In the
curved place, since such a secondary flow velocity distribution is
generated, especially when particles are included in the fluids,
the uneven distribution (mal-distribution) of the particles may
possibly arise.
In the present invention, the protruding parts are provided as
described above, so that the uneven distribution of the particles
can be suppressed and the laminar flows can be formed in a stable
way.
In the present invention, the micro fluidic device may be
manufactured by any of methods. Now, a method for fabricating the
micro fluidic device preferable and usable for the present
invention will be described below.
The micro fluidic device of the present invention is preferably
formed by laminating thin film pattern members on which prescribed
two-dimensional patterns are formed. The thin film pattern members
are more preferably laminated under a state that the surfaces of
thin films come into direct contact with each other and are bonded
together.
As a preferred method for producing the micro fluidic device of the
present invention, can be exemplified a method for producing a
micro fluidic device comprising:
(i) a step (a donor substrate forming step) of forming a plurality
of thin film pattern members respectively corresponding to
sectional forms of a predesignated micro fluidic device on the
donor substrate; and
(ii) a step (a bonding step) of repeatedly bonding the donor
substrate on which the plurality of thin film pattern members are
formed to and separating the donor substrate from a second
substrate to transfer the plurality of thin film pattern members on
the second substrate.
The method for producing the micro fluidic device of the present
invention will be described in more detail.
(Donor Substrate Forming Step)
In the present invention, a donor substrate is preferably formed by
an electro-forming method. Here, the donor substrate indicates a
substrate on which the plurality of thin film patterns respectively
corresponding to the sectional forms of the target micro fluidic
device are formed on the first substrate. The first substrate is
preferably made of metal, ceramics or silicon and metal such as
stainless steel may be preferably used.
Initially, the first substrate is coated by a thick film
photo-resist. The photo-resist is exposed by a photo-mask which
includes the sectional forms of the micro fluidic device to be
produced. Then the photo-resist is developed. Then, the substrate
having the resist patterns is immersed in a plating bath to allow,
for instance, a nickel plating to grow on the surface of the metal
substrate that is not covered with the photo-resist. The thin film
patterns may be formed with copper or nickel by using the
electro-forming method.
Then, the resist patterns are removed to form the thin film
patterns respectively corresponding to the sectional forms of the
micro fluidic device on the first substrate.
FIGS. 6A to 6C are explanatory views of the thin film patterns for
forming the part shown in FIG. 2. FIG. 6A shows a sectional form
taken along a line X-X' of the curved place shown in FIG. 2. FIG.
6A and FIG. 6B show that the micro fluidic device having three
protruding parts is formed by laminating in order a total of 11
thin film patterns including 501A.sub.1, 502B.sub.1, 502B.sub.2,
503C.sub.1, 502B.sub.3, 503C.sub.2, 502B.sub.4, 503C.sub.3,
502B.sub.5, 502B.sub.6 and 501A.sub.2.
FIG. 6C shows only a part of a curved place of the donor substrate.
The thin film patterns 501A.sub.1 and 501A.sub.2 provided on the
first substrate 500 respectively correspond to parts that form the
upper surface and the lower surface of a micro channel. The thin
film patterns 503C.sub.1, 503C.sub.2 and 503C.sub.3 correspond to
parts at which the protruding parts are located. The thin film
patterns 502B.sub.1, 502B.sub.2, 502B.sub.3, 502B.sub.4, . . . ,
correspond to parts of the micro channel in which the protruding
parts are not provided.
(Bonding Step)
The bonding step means a step for repeatedly bonding the first
substrate (the donor substrate) and the second substrate (the
target substrate) and separating the both substrate each other to
transfer the plurality of thin film patterns on the donor substrate
onto the target substrate. A bonding operation is preferably
carried out by a room-temperature bonding method or a surface
activated bonding method.
FIGS. 7A to 7F show fabrication process diagrams showing one
exemplary embodiment of the method for fabricating the micro
fluidic device that can be preferably usable for the present
invention.
First, as shown in FIG. 7A, the donor substrate 505 is attached on
a lower stage in a vacuum chamber that is not shown in the drawing.
The target substrate 510 is attached on an upper stage in the
vacuum chamber that is not shown in the drawing. Subsequently, the
air in the vacuum chamber is exhausted to obtain a high vacuum
state or an ultra-high vacuum state. Then, the lower stage is moved
relatively to the upper stage to locate the thin film pattern
501A.sub.1 of a first layer of the donor substrate 505 just below
the target substrate 510. Then, an argon atom beam is irradiated on
the surface of the target substrate 510 and the surface of the thin
film pattern 501A.sub.1 of the first layer to clean the
surfaces.
Then, as shown in FIG. 7B, the upper stage is lowered to press the
target substrate 510 and the donor substrate 505 for a prescribed
time (for instance, 5 minutes) with a prescribed load force (for
instance, 10 kgf/cm.sup.2) and the target substrate 510 is bonded
(a surface activated bonding) onto the thin film pattern 501A.sub.1
of the first layer under a room temperature. In this exemplary
embodiment, the thin film patterns are laminated in order of
501A.sub.1, 502B.sub.1, 502B.sub.2, 503C.sub.1, 502B.sub.3,
503C.sub.2, 502B.sub.4, 503C.sub.3, 502B.sub.5, 502B.sub.6 and
501A.sub.2.
Then, as shown in FIG. 7C, when the upper stage is lifted to
separate the donor substrate from the target substrate, the thin
film pattern 501A.sub.1 of the first layer is peeled off from the
first substrate (the donor substrate) 500 and transferred to the
target substrate 510 side. This phenomenon arises, because an
adhesive strength between the thin film pattern 501A.sub.1 and the
target substrate 510 is larger than an adhesive strength between
the thin film pattern 501A.sub.1 and the first substrate (the donor
substrate) 500.
After that, as shown in FIG. 7D, the lower stage is moved to locate
the thin film pattern 502B.sub.1 of a second layer on the donor
substrate 505 just below the target substrate 510. Then, the
surface of the thin film pattern 501A.sub.1 (a surface which was in
contact with the first substrate 500) transferred to the target
substrate 510 side and the surface of the thin film pattern
502B.sub.3 of the second layer are cleaned as described above.
Then, as shown in FIG. 7E, the upper stage is lowered to bond the
thin film pattern 501A.sub.1 of the first layer to the thin film
pattern 502B.sub.1 of the second layer. As shown in FIG. 7F, when
the upper stage is lifted, the thin film pattern 502B.sub.1 of the
second layer is peeled off from the metal substrate (the first
substrate) 500 and transferred to the target substrate 510
side.
The donor substrate 505 and the target substrate 510 are repeatedly
positioned, bonded to and separated from each other so that the
plurality of thin film patterns such as other thin film patterns
(502B.sub.2, 503C.sub.1, 502B.sub.3, 503C.sub.2, 502B.sub.4,
503C.sub.3, 502B.sub.5, 502B.sub.6 and 501A.sub.2) respectively
corresponding to the sectional forms of the micro fluidic device
are transferred to the target substrate. When a laminated body
transferred to the target substrate 510 is detached from the upper
stage and the target substrate 510 is removed, the micro fluidic
device shown in FIGS. 6A to 6C is obtained.
The present invention is not limited to the above-described
exemplary embodiment and may be variously modified within a range
without departing the gist of the present invention. The components
of the exemplary embodiments may be arbitrarily combined within the
range without departing the gist of the present invention.
In the above-described exemplary embodiments, the donor substrate
is manufactured by using the electro-forming method, however, the
donor substrate may be formed by using a semiconductor process. For
instance, a substrate made of a Si wafer is prepared. On this
substrate, a mold releasing layer made of polyimide is formed by a
spin coating method. On the surface of the mold releasing layer, an
Al thin film as a component material of a micro fluidic device is
formed by a sputtering method. The aluminum thin film is patterned
by a photo-lithography method so that the donor substrate can be
formed.
* * * * *